Residential electrical systems are typically served by a variety of different transmission and distribution cables. For example, with communication equipment, entertainment equipment, alarm equipment, etc., each must be connected via numerous power lines, control lines, and analog and digital communication lines. A confusion of incoming cables often results.
Hybrid branch cables were introduced to eliminate the clutter of discrete cables. Hybrid branch cables are singular cables which carry a multitude of internal conductors. The conductors are devoted to different purposes including 110 volt, 60 Hz power, data communication, and control. U.S. Pat. No. 5,053,583 issued to Miller et al. discloses an exemplary bundled hybrid ribbon cable in which a flat ribbon cable of multiple conductors is rolled and bundled in a generally tubular outer casing. The ribbon cable provides for ease of termination while the bundled tubular configuration facilitates installation and routing of the hybrid cable through the framework of the dwelling.
To further facilitate installation, hybrid branch cables must be as flexible as possible. However, the various signal conductors, power conductors, etc., all detract from the cable's flexibility. Moreover, the close proximity of the internal conductors generates cross-talk, and this necessitates an internal shield which further detracts from the flexibility of the cable. For example, the intertwined foil layer suggested in the above-described '583 patent severely increases the rigidity of the cable along its axis.
U.S. Pat. No. 5,097,099 issued to Miller discloses a partial solution in the form of a composite fiber shield. The composite shield serves to protect the conductors from electromagnetic interference (EMI), yet the fibrous nature does not severely limit the axial rigidity of the bundled cable. The proposed improvement is limited to the shield. This leaves room for further flexibility of other components of the cable.
More specifically, the manufacture of hybrid bundled cables includes rolling of the ribbon cable prior to encasement in the outer shell. The installation and repair of such cables requires stripping of the shell, unrolling of the ribbon cable and positioning of the conductors. Given the frequent need to manipulate the internal ribbon cable, it would be greatly advantageous to increase its flexibility to facilitate folding and unfolding. The present invention provides an innovative solution.